Production of carbon nanotube modified battery electrode powders via single step dispersion

ABSTRACT

Methods of making single walled carbon nanotubes (SWNTs) including a single step for preparing a homogeneous dispersion of SWNTs in a battery electrode powder. The method may comprise providing a reactor in fluid communication with a mixer, wherein an aerosol containing SWNTs is transmitted from the reactor directly to the mixer containing a battery electrode powder.

FIELD

The present disclosure relates generally to a method of making single walled carbon nanotubes (SWNTs). The method includes a single step for preparing a homogeneous dispersion of SWNTs in a battery electrode powder.

BACKGROUND

SWNTs provide numerous benefits for use in, for example, electrically and thermally conducting functional materials. In many cases, SWNTs are dispersed in a battery electrode powder material to produce carbon-reinforced composite materials, which often possess improved properties relative to the corresponding non-composite materials.

However, current dispersion technologies are not only expensive but also degrade nanotube properties, leading to reduction of aspect ratio and introduction of defects. The technologies end up requiring more nanotube loading (in terms of weight percent) for improved performance. In addition, current technologies often result in high levels of SWNT agglomeration within the composite materials.

There is thus a need in the art for a more efficient method for preparing SWNT-containing dispersions that preferably reduce SWNT agglomeration.

SUMMARY

The present disclosure relates generally to methods of making SWNTs which, for example, may be used as additives in composite materials, such as for use in battery electrodes. In particular, the present disclosure provides a single step method for preparing a homogeneous dispersion of SWNTs in a battery electrode powder. The method may comprise providing a reactor in fluid communication with a mixer, wherein an aerosol containing SWNTs is transmitted from the reactor directly to the mixer containing a battery electrode powder.

Aspects of the present disclosure also relate to SWNTs, SWNT-containing dispersions, and composite materials including the SWNTs obtainable by the methods disclosed herein. Further, aspects of the present disclosure also relate to apparatuses for preparing SWNT-containing dispersions as described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example apparatus for preparing SWNT-containing dispersions according to aspects of the present invention.

FIG. 2 shows a flowchart depicting an example method for preparing SWNT-containing dispersions according to aspects of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present disclosure relates generally to methods of making SWNTs which, for example, may be used as additives in composite materials, such as for use in battery electrodes. In particular, the present disclosure provides a single step method for preparing a homogeneous dispersion of SWNTs in a battery electrode powder. The method may comprise providing a reactor in fluid communication with a mixer, wherein an aerosol containing SWNTs is transmitted from the reactor directly to the mixer containing a battery electrode powder.

The method of the present disclosure comprises providing a reactor for preparing an aerosol of SWNTs. According to some aspects, the reactor is configured for use with a chemical vapor deposition (CVD) method for the preparation of SWNTs.

The reactor may be in fluid communication with a source of catalyst and/or catalyst precursor and a carbon source. For example, as shown in FIG. 1, the reactor 1 may be in fluid communication with a source chamber 2, the source chamber 2 being configured to house a catalyst and/or catalyst precursor and/or a carbon source. According to some aspects, the reactor may be in fluid communication with one or more source chambers. For example, the catalyst and/or catalyst precursor and/or the carbon source gas may be housed in different or the same source chambers.

The method may comprise injecting the catalyst and/or catalyst precursor and the carbon source into the reactor. For example, the reactor may be provided with a first inlet for injecting the catalyst and/or catalyst precursor from the source chamber to the reactor. The first inlet may be in communication with, for example, a liquid pump 3 as shown in FIG. 1, which may pump the catalyst and/or catalyst precursor from the source chamber 2 to the reactor 1.

As used herein, the term “catalyst” refers to a component that provokes or speeds up a chemical reaction, for example, the synthesis of SWNTs. The catalyst may comprise, for example, a metal. Examples of metals include, but are not limited to, transition metals, lanthanide metals, actinide metals, and combinations thereof. For example, the catalyst may comprise a transition metal such as chromium (Cr), molybdenum (Mo), tungsten (W), iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), copper (Cu), silver (Ag), gold (Au), cadmium (Cd), scandium (Sc), yttrium (Y), lanthanum (La), platinum (Pt), and/or combinations thereof.

According to some aspects, a catalyst precursor may be injected into the reactor, either in place of or in combination with a catalyst. As used herein, the term “catalyst precursor” refers to a component that can be converted into an active catalyst. Examples of catalyst precursors include, but are not limited to, transition metal salts, such as a nitrate, acetate, citrate, chloride, fluoride, bromide, iodide, and/or hydrates thereof. For example, the catalyst precursor may be a metallocene, a metal acetylacetonate, a metal phthalocyanine, a metal porphyrin, a metal salt, a metalorganic compound, a metal sulfate, a metal hydroxide, a metal carbonate, or a combination thereof.

According to some aspects, a catalyst may be produced from the catalyst precursor inside the reactor. For example, after the catalyst precursor has been injected into the reactor, a component or all of the catalyst precursor, such as a metal, may be reduced into an active catalyst prior to the production of SWNTs. The reactor may comprise a first region wherein the catalyst may be produced.

According to some aspects, the catalyst and/or catalyst precursor may be provided as a nanoparticle. For example, the catalyst and/or catalyst precursor may have a diameter from about 0.01 to 500 nm, preferably from about 0.01 to 250 nm, even more preferably from about 0.05 to 200 nm, and most preferably from about 0.5 to 100 nm.

According to some aspects, the catalyst and/or catalyst precursor may be injected into the reactor as a liquid, spray, or aerosol. For example, the catalyst and/or catalyst precursor may be mixed with a first carrier gas, such as an inert gas, prior to injection into the reactor. Examples of inert gasses include, but are not limited to, argon gas, hydrogen gas, helium gas, nitrogen gas, and mixtures thereof. For example, as shown in FIG. 1, the catalyst and/or catalyst precursor may be combined with hydrogen gas prior to injection into the reactor.

The method may also comprise injecting the carbon source into the reactor. According to some aspects, the reactor may be provided with a second inlet for injecting the carbon source from the source chamber to the reactor. The second inlet may be the same or different from the first inlet. The second inlet may be in communication with a liquid pump, which may pump the carbon source from the source chamber to the reactor.

Examples of carbon sources include, but are not limited to, a hydrocarbon, an alcohol, an ester, a ketone, an aromatic, an aldehyde, and a combination thereof. For example, the carbon source may be selected from xylene, propane, butane, butene, ethylene, ethanol, carbon monoxide, butadiene, pentane, pentene, methane, ethane, acetylene, carbon dioxide, naphthalene, hexane, cyclohexane, benzene, methanol, propanol, propylene, commercial fuel gases (such as liquefied petroleum gas, natural gas, and the like), and combinations thereof.

According to some aspects, the carbon source may be injected as a liquid, spray, or aerosol. For example, the carbon source may be mixed with a second carrier gas, wherein the second carrier gas is the same or different than the first carrier gas. The carbon source may be injected into the reactor before, after, or simultaneously with the catalyst and/or catalyst precursor.

According to some aspects, an aerosol of SWNTs may be produced in the reactor. For example, the carbon source may decompose at the surface of the catalyst particles in the reactor by thermal and/or catalytic decomposition, thereby resulting in the formation and/or growth of SWNTs.

According to some aspects, the temperature of the reactor may be maintained and/or varied using one or more heat sources, such as a furnace. As shown in FIG. 1, the furnace 4 may be proximal to the reactor 1. For example, the furnace 4 may be proximal to one, two, or more sides of one or more portions of reactor 1, or may completely surround one or more portions of reactor 1.

The one or more heat sources may maintain the temperature of the reactor 1 at a temperature suitable for one or more of the reactions described herein. For example, the furnace 4 may maintain the temperature of the reactor at a temperature suitable for reducing the catalyst precursor into active catalyst and/or for the synthesis and/or formation of SWNTs.

According to some aspects, different regions of the reactor 1 may be maintained at different temperatures. For example, the first region of the reactor may be maintained at a temperature suitable for reducing the catalyst precursor into active catalyst and a second region of the reactor may be maintained at a temperature suitable for the synthesis and/or growth of SWNTs. According to some aspects, each region of the reactor 1 may be heated by the same and/or different heat sources.

According to some aspects, the one or more heat sources may maintain the temperature of the reactor at a temperature of between about 200 and 1600° C.

The SWNTs may be present in the reactor as an aerosol. The method may comprise directly transmitting the SWNT-containing aerosol from the reactor to a mixer, the mixer comprising a battery electrode powder. For example, as shown in FIG. 1, a mixer 5 may be provided in fluid communication with the reactor 1. The mixer 5 may be above, below, or beside the reactor 1. According to some aspects, the aerosol may be continuously introduced to the mixer as the SWNTs are synthesized. Alternatively, the SWNT-containing aerosol may be introduced to the mixer once a portion or all of the SWNTs have been synthesized.

According to some aspects, the battery electrode powder may be any material capable of providing a dispersed SWNT material. For example, the battery electrode powder may comprise a primary battery electrode powder material. As used herein, the term “primary battery electrode powder material” refers to the most prominent material present in the battery electrode powder, such as the material having the highest weight percentage of all the materials making up the battery electrode powder. According to some aspects, the primary battery electrode powder material may comprise a liquid such as a metal alloy, a carbon pitch, a solution of dispersed graphene or graphene oxide sheets, a tar, a cement, an asphalt, an ionic liquid selected from a imidazolium-based liquid, an organic solvent (for example, N,N-dimethylformamide or n-methylpyrrolidone), a melted polymer (for example, a melted polyester, epoxy, polyimide, organosilicone, nylon, Teflon, polystyrene, polyethylene, or a combination thereof), or a combination thereof.

According to some aspects, the battery electrode powder may also comprise one or more secondary battery electrode powder materials. As used herein, the term “secondary battery electrode powder material” refers to one or more components of the battery electrode powder present in lesser amounts than the primary battery electrode powder material.

According to some aspects, the secondary battery electrode powder material may comprise a surfactant, such as an anionic surfactant. Examples of anionic surfactants include, but are not limited to, sodium dodecyl sulfate (SDS), salts of carboxylic acids, salts of sulfonic acids, salts of sulfuric acid, dodecyltrimethylammonium bromide, sodium octylbenzene sulfonate, phosphoric and polyphosphoric acid esters, alkylphosphates, monoalkyl phosphate (MAP), sodium butylbenzene sulfonate, sodium benzoate, and salts of perfluorocarboxylic acids.

According to some aspects, the secondary material may comprise a binder. Examples of binders include, but are not limited to, fluorine resins (for example, polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVdF)), polyacrylonitrile (PAN), polyimide resins, acrylic resins, polyolefin resins, or a combination thereof.

According to some aspects, the SWNT-containing aerosol may comprise one or more carrier gasses that carry the SWNTs from the reactor to the mixer. For example, the carrier gasses may be the same as the first and/or second carrier gas used to inject the catalyst and/or catalyst precursor and/or the carbon source into the reactor. According to some aspects, an additional carrier gas may be injected into or already present in the reactor. The additional carrier gas may be the same or different from the first and/or second carrier gas. For example, as shown in FIG. 1, the reactor may comprise a carrier gas inlet 6 wherein an additional carrier gas, such as a helium gas, is injected into the reactor. According to some aspects, the mixer 5 may be provided with an outlet 11 to allow the one or more carrier gasses to be released as the SWNTs are dispersed within the battery electrode powder.

The method comprises dispersing the SWNTs in the battery electrode powder. For example, the mixer may be provided with a dispersing component, such as a mechanical stirrer, a magnetic stirrer, a ball miller, a sonicator, or a combination thereof. For example, as shown in FIG. 1, the mixer 5 may include a stirrer 7 configured to disperse the SWNTs 8 in a battery electrode powder comprising the primary battery electrode powder material 9 and the secondary materials 10. According to some aspects, the SWNTs may be transmitted to the mixer under constant stirring.

According to some aspects, the amount of any of the components herein may be selected in order to provide a specific ratio of SWNT to battery electrode powder. The specific ratio may be selected in order to provide a low instance of SWNT agglomeration in the battery electrode powder. For example, the ratio of SWNT to battery electrode powder by weight may be from about 0.01 to 100 wt %, preferably from about 0.01 to 80 wt %, more preferably from about 0.01 to 65 wt %, and most preferably from about 0.01 to 50 wt %.

According to some aspects, the method may also optionally comprise mixing the resultant dispersion with an active material and/or making a slurry comprising the dispersion using commonly established methods.

The present disclosure also relates to SWNTs, SWNT-containing dispersions, and composite materials including the SWNTs and/or SWNT-containing dispersions obtainable by the methods disclosed herein. For example, the present disclosure relates to battery electrodes comprising the composite materials described herein.

The present disclosure also relates to an apparatus for preparing SWNT-containing dispersions as described herein. It should be understood that the elements of the apparatus described herein may be arranged in various ways (e.g., above, below, beside one another) so long as they do not depart from the functionalities described herein.

While the aspects described herein have been described in conjunction with the example aspects outlined above, various alternatives, modifications, variations, improvements, and/or substantial equivalents, whether known or that are or may be presently unforeseen, may become apparent to those having at least ordinary skill in the art. Accordingly, the example aspects, as set forth above, are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the disclosure. Therefore, the disclosure is intended to embrace all known or later-developed alternatives, modifications, variations, improvements, and/or substantial equivalents.

Thus, the claims are not intended to be limited to the aspects shown herein, but are to be accorded the full scope consistent with the language of the claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed as a means plus function unless the element is expressly recited using the phrase “means for.”

Further, the word “example” is used herein to mean “serving as an example, instance, or illustration.” Any aspect described herein as “example” is not necessarily to be construed as preferred or advantageous over other aspects. Unless specifically stated otherwise, the term “some” refers to one or more. Combinations such as “at least one of A, B, or C,” “at least one of A, B, and C,” and “A, B, C, or any combination thereof” include any combination of A, B, and/or C, and may include multiples of A, multiples of B, or multiples of C. Specifically, combinations such as “at least one of A, B, or C,” “at least one of A, B, and C,” and “A, B, C, or any combination thereof” may be A only, B only, C only, A and B, A and C, B and C, or A and B and C, where any such combinations may contain one or more member or members of A, B, or C. Nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. 

The invention claimed is:
 1. A method for preparing a dispersion of single walled carbon nanotubes in a battery electrode powder, the method comprising: preparing an aerosol containing single walled carbon nanotubes in a reactor; and transmitting the aerosol directly from the reactor to a mixer containing the battery electrode powder to produce the dispersion, wherein the battery electrode powder comprises a primary battery electrode powder material and a secondary material, the secondary material being a surfactant optionally together with a binder, wherein a ratio of single walled carbon nanotubes to battery electrode powder is from about 0.01 to 50 wt %; and wherein the surfactant comprises sodium dodecyl sulfate, wherein the aerosol is continuously transmitted to the mixer as the single walled carbon nanotubes are prodiced in the reactor.
 2. The method according to claim 1, wherein the primary battery electrode powder material comprises an organic solvent.
 3. The method according to claim 2, wherein the organic solvent comprises n-methylpyrrolidone.
 4. The method according to claim 1, wherein the battery electrode powder is continually mixed as the aerosol is transmitted to the mixer.
 5. The method according to claim 4, wherein the battery electrode powder is continually mixed by a mechanical stirrer, a magnetic stirrer, a ball miller, a sonicator, or a combination thereof provided as part of the mixer.
 6. The method according to claim 1, wherein the single walled carbon nanotubes are produced by contacting a carbon source and a catalyst in the reactor.
 7. The method according to claim 6, wherein the catalyst comprises a metal.
 8. The method according to claim 6, wherein a catalyst precursor is converted to the catalyst in the reactor.
 9. The method according to claim 6, wherein the catalyst comprises nanoparticles.
 10. A method for preparing a dispersion of single walled carbon nanotubes in a battery electrode powder, the method comprising: preparing an aerosol containing single walled carbon nanotubes in a reactor; and transmitting the aerosol directly from the reactor to a mixer containing the battery electrode powder to produce the dispersion, wherein the battery electrode powder comprises a primary battery electrode powder material and a secondary material, the secondary material being an anionic surfactant optionally together with a binder, and wherein a ratio of single walled carbon nanotubes to battery electrode powder is from about 0.01 to 50 wt %, and wherein the aerosol is continuously transmitted to the mixer as the single walled carbon nanotubes are produced in the reactor. 